blob: 1ee40eb9a2c05cc1751828af612c6942758b4c72 [file] [log] [blame]
Al Viro3e93cd62009-03-29 19:00:13 -04001#include <linux/module.h>
2#include <linux/sched.h>
3#include <linux/fs.h>
4#include <linux/path.h>
5#include <linux/slab.h>
Al Viro5ad4e532009-03-29 19:50:06 -04006#include <linux/fs_struct.h>
Al Viro3e93cd62009-03-29 19:00:13 -04007
8/*
9 * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values.
10 * It can block.
11 */
12void set_fs_root(struct fs_struct *fs, struct path *path)
13{
14 struct path old_root;
15
16 write_lock(&fs->lock);
17 old_root = fs->root;
18 fs->root = *path;
19 path_get(path);
20 write_unlock(&fs->lock);
21 if (old_root.dentry)
22 path_put(&old_root);
23}
24
25/*
26 * Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values.
27 * It can block.
28 */
29void set_fs_pwd(struct fs_struct *fs, struct path *path)
30{
31 struct path old_pwd;
32
33 write_lock(&fs->lock);
34 old_pwd = fs->pwd;
35 fs->pwd = *path;
36 path_get(path);
37 write_unlock(&fs->lock);
38
39 if (old_pwd.dentry)
40 path_put(&old_pwd);
41}
42
43void chroot_fs_refs(struct path *old_root, struct path *new_root)
44{
45 struct task_struct *g, *p;
46 struct fs_struct *fs;
47 int count = 0;
48
49 read_lock(&tasklist_lock);
50 do_each_thread(g, p) {
51 task_lock(p);
52 fs = p->fs;
53 if (fs) {
54 write_lock(&fs->lock);
55 if (fs->root.dentry == old_root->dentry
56 && fs->root.mnt == old_root->mnt) {
57 path_get(new_root);
58 fs->root = *new_root;
59 count++;
60 }
61 if (fs->pwd.dentry == old_root->dentry
62 && fs->pwd.mnt == old_root->mnt) {
63 path_get(new_root);
64 fs->pwd = *new_root;
65 count++;
66 }
67 write_unlock(&fs->lock);
68 }
69 task_unlock(p);
70 } while_each_thread(g, p);
71 read_unlock(&tasklist_lock);
72 while (count--)
73 path_put(old_root);
74}
75
Al Viro498052b2009-03-30 07:20:30 -040076void free_fs_struct(struct fs_struct *fs)
Al Viro3e93cd62009-03-29 19:00:13 -040077{
Al Viro498052b2009-03-30 07:20:30 -040078 path_put(&fs->root);
79 path_put(&fs->pwd);
80 kmem_cache_free(fs_cachep, fs);
Al Viro3e93cd62009-03-29 19:00:13 -040081}
82
83void exit_fs(struct task_struct *tsk)
84{
Al Viro498052b2009-03-30 07:20:30 -040085 struct fs_struct *fs = tsk->fs;
Al Viro3e93cd62009-03-29 19:00:13 -040086
87 if (fs) {
Al Viro498052b2009-03-30 07:20:30 -040088 int kill;
Al Viro3e93cd62009-03-29 19:00:13 -040089 task_lock(tsk);
Al Viro498052b2009-03-30 07:20:30 -040090 write_lock(&fs->lock);
Al Viro3e93cd62009-03-29 19:00:13 -040091 tsk->fs = NULL;
Al Viro498052b2009-03-30 07:20:30 -040092 kill = !--fs->users;
93 write_unlock(&fs->lock);
Al Viro3e93cd62009-03-29 19:00:13 -040094 task_unlock(tsk);
Al Viro498052b2009-03-30 07:20:30 -040095 if (kill)
96 free_fs_struct(fs);
Al Viro3e93cd62009-03-29 19:00:13 -040097 }
98}
99
100struct fs_struct *copy_fs_struct(struct fs_struct *old)
101{
102 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
103 /* We don't need to lock fs - think why ;-) */
104 if (fs) {
Al Viro498052b2009-03-30 07:20:30 -0400105 fs->users = 1;
106 fs->in_exec = 0;
Al Viro3e93cd62009-03-29 19:00:13 -0400107 rwlock_init(&fs->lock);
108 fs->umask = old->umask;
Miklos Szeredif7ad3c62010-08-10 11:41:36 +0200109 get_fs_root_and_pwd(old, &fs->root, &fs->pwd);
Al Viro3e93cd62009-03-29 19:00:13 -0400110 }
111 return fs;
112}
113
114int unshare_fs_struct(void)
115{
Al Viro498052b2009-03-30 07:20:30 -0400116 struct fs_struct *fs = current->fs;
117 struct fs_struct *new_fs = copy_fs_struct(fs);
118 int kill;
119
120 if (!new_fs)
Al Viro3e93cd62009-03-29 19:00:13 -0400121 return -ENOMEM;
Al Viro498052b2009-03-30 07:20:30 -0400122
123 task_lock(current);
124 write_lock(&fs->lock);
125 kill = !--fs->users;
126 current->fs = new_fs;
127 write_unlock(&fs->lock);
128 task_unlock(current);
129
130 if (kill)
131 free_fs_struct(fs);
132
Al Viro3e93cd62009-03-29 19:00:13 -0400133 return 0;
134}
135EXPORT_SYMBOL_GPL(unshare_fs_struct);
136
Al Viroce3b0f82009-03-29 19:08:22 -0400137int current_umask(void)
138{
139 return current->fs->umask;
140}
141EXPORT_SYMBOL(current_umask);
142
Al Viro3e93cd62009-03-29 19:00:13 -0400143/* to be mentioned only in INIT_TASK */
144struct fs_struct init_fs = {
Al Viro498052b2009-03-30 07:20:30 -0400145 .users = 1,
Al Viro3e93cd62009-03-29 19:00:13 -0400146 .lock = __RW_LOCK_UNLOCKED(init_fs.lock),
147 .umask = 0022,
148};
149
150void daemonize_fs_struct(void)
151{
Al Viro498052b2009-03-30 07:20:30 -0400152 struct fs_struct *fs = current->fs;
Al Viro3e93cd62009-03-29 19:00:13 -0400153
Al Viro498052b2009-03-30 07:20:30 -0400154 if (fs) {
155 int kill;
156
157 task_lock(current);
158
159 write_lock(&init_fs.lock);
160 init_fs.users++;
161 write_unlock(&init_fs.lock);
162
163 write_lock(&fs->lock);
164 current->fs = &init_fs;
165 kill = !--fs->users;
166 write_unlock(&fs->lock);
167
168 task_unlock(current);
169 if (kill)
170 free_fs_struct(fs);
171 }
Al Viro3e93cd62009-03-29 19:00:13 -0400172}